The piloting experiment (RB 820239) on VESUVIO on (NH4)2PdCl6, has shown that, at 5 and 80K, H momentum distribution, J(y), in NH4+ is non-Gaussian with non-vanishing excess-kurtosis. The following experiment (RB 10065) has recently been performed on (ND4)2PdCl6 where the preliminary analysis shows the same effect for D at 5K and 300K. Unfortunately, due to beam losses during last 3 cycles at ISIS, the planned scientific programme could not be realized. This continuation experiment will aim at putting the lacking pieces of information about the transition from quantum rotation tunnelling to classical motional regime of ammonium ions. The following experiments will be performed: (i) (ND4)2PdCl6 at 5, 80 and 300K, (ii) (NH4)2PdCl6 at 300K, (iii) (NH4)2TeCl6 at 5, 80 and 300K. New YAP detectors will be used with much improved energy resolution enabling much better analysis of J(y).